Back Rest for a Stool or a Chair, and Stool or Chair Provided with such a Back Rest

ABSTRACT

The invention relates to a back rest for a stool or a chair, comprising two adjacent, spring-mounted back supports ( 3.1 ), each of which is fixed to a separate carrier part ( 4.1 ). Said back rest is characterised in that each carrier part ( 4.1 ) forms the first limb of an essentially L-shaped carrier ( 4 ), and the second limb ( 4.2 ) of each carrier ( 4 ) is fixed beneath the stool or chair seat in such a way that it can be pivoted about a horizontal axis against an elastic force.

The invention concerns a backrest for a stool or chair with two backsupports that are positioned laterally adjacent to one another and aresupported in a springy fashion, wherein each one is connected to aseparate carrier part.

In such a backrest, disclosed in DE 90 06 316 U1, each back support isprovided on a separate carrier part. The carrier parts are positionedrelative to one another in a V-shape and the lower ends of these carrierparts are attached to the rear of the seat on the chair frame. Eventhough the back supports, as a result of the springy properties of theirtwo carrier parts, provide movability to some degree in order to adjustto the different seated positions of a seated person, it has been foundthat this construction is unable to relieve the backbone of a seatedperson for extended periods of time of being seated in changing seatedpositions as well as of individual persons having greatly varyingphysical build.

It is an object of the present invention to design a backrest for a seator a chair in such a way that the seated person in different seatedpositions is supported optimally in the area of the back or backbone.

As a solution to this object, it is provided according to claim 1 thateach carrier part forms the first leg of a substantially L-shapedsupport member and that the second leg of each support member ispivotable underneath the stool or chair seat against a spring forceabout a horizontal axis. In this way, it is ensured that each backsupport optimally follows the back movement as a function of thedifferent movements or seated positions of a seated person withoutlosing their support function.

In order to achieve that a seated person is optimally supported even fora lateral movement or a lateral as well as rearwardly oriented movement,according to further invention it is provided that the support membersare connected to one another by a guide bar that is oriented in the restposition substantially perpendicularly to the support members, whereinthe guide bar is supported in or on the seat understructure andconnected to the support member in such a way that upon displacement ofone back support to the front or to the rear the other back support ismoved in the opposite direction, respectively, wherein, for preventing a“jump” between the two back supports, they are preferably connected in aspringy fashion to the support members in such a way that asubstantially uniform continuous backrest is present.

The guide bar is preferably pivotably connected with its ends to thesupport members and, moreover, is pivotably supported on the seat orseat understructure between its pivot points on the support members.

Further preferred embodiments of the invention are disclosed in thedependant claims.

The invention will be disclosed in the following with reference to theattached drawings.

FIG. 1 shows a view of a backrest that is fastened to a post of a chairor stool that is not shown otherwise.

FIG. 2 shows a view of a modified embodiment of a backrest.

FIG. 3 shows a view of a further modified embodiment of a backrest.

FIG. 4 shows an embodiment of the type of attachment of a backrest onits carrier part.

FIG. 5 shows an exploded view of the embodiment according to FIG. 4.

FIG. 6 shows an embodiment of the type of attachment of the supportmember of the back support on the post of a chair or stool.

FIG. 7 shows an isometric illustration of a chair.

FIG. 8 shows a detail in isometric illustration of the column of thechair with attached seat frame on which the support members for the backsupports are pivotably attached.

FIG. 9 shows in isometric illustration a plan view onto the seatunderstructure connected to the seat frame.

FIG. 10 shows for illustration of the inventive principle a schematicpartial view of the backrest construction in correlation to the seatunderstructure.

FIG. 7 shows an isometric view of a chair, comprised of a five star base1.1 provided with coasters, a column 1 supported on the five star base,a seat 100, and a backrest 3 with two back supports 3.1 arrangedlaterally at a spacing from one another and connected to L-shapedsupport members 4 that are each comprised of a substantially verticallyarranged carrier part 4.1 and a carrier part 4.2 that is substantiallyhorizontally arranged. Each back support 3.1 is attached to a securingmember 7 that is adjustable along the correlated carrier part 4.1 so asto assume different height-adjusted positions. Each securing member 7comprises rubber elements such that the individual back supports aremovable relative to the carrier part 4.1. The carrier parts 4.1 areconnected to one another by an elastically deformable transverse stay 9having a spring stiffness that is designed such that free movability ofthe individual back support relative to the other back support ismaintained to a limited extent.

According to FIGS. 1 to 3, the carrier parts 4.2 are pivotably supportedby means of a support unit 2 about a horizontal pivot axis 5. Thecarrier parts 4.2 of the support member 4 are embodied as two-partlevers, wherein a substantially vertically oriented spring element 6acts on the free lever end 4.3 of the lever and wherein the force of thespring element acting on the support member is changeable. This springelement 6 can be a tension spring, a pneumatic or hydraulic springelement or the like.

Catch openings 8 provided in the area of the carrier parts 4.1 makeapparent that the securing members 7 are height-adjustably mounted onthe carrier parts 4.1. According to FIG. 2, the back supports 3.1 areconnected approximately at their center by an elastically deformabletransverse stay 3.2 whose strength is designed such that the backsupports 3.1 maintain their function as individual supports wherein thefree movability of one back support relative to the other back supportis maintained to a limited extent.

According to FIG. 3 the two back supports 3.1 each are also attached ontheir own carrier parts 4.1 of the support members 4 so as to be springyindividually. In this embodiment of the backrest the securing members 7are designed such that the upper ends of the carrier parts 4.1 projectupwardly past the securing member 7. The free ends of the carrier parts4.1 are connected to one another by an elastically deformable transversestay 9.

FIG. 6 shows a modified embodiment of the support member that ispivotable about a horizontal axis. In or on the support unit 2 ahorizontal shaft 20 is provided that has opposite threads; on it, thesecond legs 4.2 of the support member 4 are pivotably supported. Eachleg 4.2 is embodied as a two-arm lever whose free lever end 4.4 is bentupwardly and has a substantially horizontally oriented tension spring 22attached thereto. For changing the force acting on the support members,the tension springs 22 are attached with their ends on an adjustingmember 23 that is adjustable relative to a horizontal axis at differentspacings; it supports, for example, a nut 24 that is engaged by athreaded pin 25 that is turnable by means of a knurled wheel 26. Eachleg 4.2 supports in the area of its bearing location on the shaft 20 athreaded bushing 27 in such a way that upon rotation of the shaft 20 asa result of the opposite threaded sections of this shaft the two legs4.2 will be adjusted relative to one another laterally so that thespacing between the back supports 3.1 according to FIGS. 1 and 3 can beadjusted.

FIGS. 8 and 9 show details of the seat frame 38 attached to the upperend of the column 1 on which the two support members 4 in the area ofthe free ends of the carrier parts 4.2 are attached so as to bepivotable about the schematically illustrated pivot axis 39. On the seatframe 38 a substantially box-shaped seat understructure 40 is fastened,for example, by screws 41 that are guided in slotted holes 42 in such away that the seat understructure 40, relative to the seat frame 38, canbe moved forward and backward.

The inventive principle of this construction will be explained in thefollowing with the aid of the schematic illustration of FIG. 9.

The principal idea of the teaching of the present invention residessubstantially in that the two back supports 3.1 are coupled to oneanother such that upon change of the seated position of the personseated on the chair (stool) a movement of one back support, for example,to the rear causes a forced movement of the other back support to thefront. As a result of the springy suspension of the back supports on thesupport members 4 the two back supports 3.1 are able to assume aposition such that a substantially uniform continuous backrest isprovided when the user of the stool or chair upon laterally recliningwill rest more strongly or push more strongly against one back support3.1, in FIG. 9 the one to the right, than against the other back support3.1. The forced coupling of the two back supports 3.1 to performoppositely oriented movements is effected by means of a guide bar 43that, in the rest position, is substantially perpendicularly orientedrelative to the support members 4; the guide bar is supported in or onthe seat understructure 40 and connected to the support parts 4.2 insuch a way that upon rearward movement of one back support 3.1 the otherback support is moved in the opposite direction, i.e., to the front. InFIG. 9 the deflection angle of the guide bar 43 relative to the centralposition is illustrated in an exaggerated way for explaining the actionprinciple. In reality, the deflection angle is only minimal so that uponpivoting the ends of the guide bar 43 carry out only very minimalmovements that are in the range of tenth of millimeters and, in thisway, are compensated by the tolerances of the construction.

The ends of the guide bar 43 are connected to the respective carrierparts 4.2, for example, by means of ball joints 44 schematicallyillustrated in FIG. 8 b which are preferably supported in elasticallydeformable sleeves 44.1. The guide bar 43 is also preferably pivotablysupported by means of ball joints 45 illustrated in FIG. 9 a in or onthe longitudinal support 40.2 of the seat understructure 50 in thecentral area between its connecting points on the carrier parts 4.2.

The carrier parts 4.2 are supported by means of coil springs 46 arrangedon the seat understructure 40 such that the two back supports 3.1 in theunloaded rest position have the same spacing from the seatunderstructure 40 and the guide bar 43 is in a rest or middle position.

According to FIG. 8, the carrier parts 4.2 have upwardly orientedprojections 47 on which the guide bar 43 is connected pivotably.Pressure plates 48 adjoin the projections 47 that by means of plungers49 passing through the frame 40.1 of the box-shaped seat understructure40 are supported on the coil springs 46 that are arrangedperpendicularly to the pivot axis 39 in the seat understructure 40. Thecoil springs 46 are supported on blocks 50 that are slidable in thelongitudinal direction of the springs and, in turn, are seated on cams52 of a camshaft 51 that is turnable by means of a handle 53 in order tochange by rotation of the cams 52 the pretension of the springs 46.

The guide bar 43 is guided in the frame 40.1 of the seat understructure40 in an arc-shaped guide groove 54 whose imaginary axes are parallel tothe pivot axis 39 of the support members 4 and relative to the front ofthe chair are curved from top toward the bottom and toward the rear.

The guide groove 54 enables a pivoting or a tilting movement of theguide bar 43 in the area of the ball joints 45 in such a way that, whenpivoting of the carrier part 4.2 to the rear, this carrier part is alsopivoted downwardly while at the same time the opposite support part 4.2is pivoted with opposite movements.

FIG. 8 shows a position of the two carrier parts 4.2 in a centralposition in which they are substantially parallel to one another whenthe two back supports 3.1 are either not loaded or uniformly loaded.

When a user with uniform loading of both back supports 3.1 reclinesbackwardly, the guide bar 43 follows this rearward movement so that as aresult of the pivotable support action of the guide bar 43 in or on thelongitudinal support 40.2 the entire seat understructure 40 is pulled,on the one hand, to the rear and, on the other hand, its rear area ispivoted downward or lowered simultaneously; this is done in accordancewith a partial seat support action disclosed in DE 299 08 599 U1 withsynchronizing mechanism and, as this structure is known, is not theobject of the present invention.

Such a synchronizing mechanism serves for pivoting the seat inaccordance with a predetermined angle ratio when pivoting the backrestto the front or to the rear.

The rearwardly oriented movement of the seat understructure 40 isrealized against the force of pressure springs 60 that are supportedbetween a support plate 61 that is stationary and forms part of the seatframe 38 and a support surface that is part of the movable seatunderstructure 40.

The FIGS. 4 and 5 show how the securing member 7 is attached to a backsupport in order to enable pivot movements of this back support 3.1relative to the securing member 7 about a vertical axis as well as ahorizontal axis. A main body 10 that is box-shaped and open in theupward and downward direction is provided at the end facing the securingmember 7 with two wall sections 10.1 that are positioned at a spacing toone another and are preferably triangular in shape; they have opposedbearing openings 10.11. On the securing member 7 a horizontally orientedbearing bushing 11 is mounted so that after passing the axle pin 12through the bearing bushings 11 aligned with the bearing openings 10.11the main body 10 is pivotably connected to the securing member 7.According to FIG. 5, in the space between the main body 10 and thesecuring member 7 a rubber stop 14 is positioned that is provided with arecess 14.1 that is matched to the shape of the bearing bushing 11. Thespring stiffness of the rubber stop is designed such that a controlledpivot movement of the main body 10 about the horizontal axis 2 that isdefined by the axle pin 12 is possible.

The main body 10 is provided on the side facing away from the securingmember 7 with an opening that is delimited upwardly and downwardly bywall sections 10.2. The wall sections 10.2 are provided with bearingopenings 10.21. A fastening element 13 that can be screwed fixedly tothe back of each back support 3.1 has a vertically oriented bearingbushing 13.1 that supports a radially outwardly projecting partition13.2. When the bearing bushing 13.1 is aligned with the bearing openings10.21, an axle pin 14.2 can be passed through these bearing openings10.21 and the bearing bushing 13.1 so that the main body 10 is attachedso as to be pivotable about a vertical axis on the fastening element 13.The partition 13.2 limits within the sleeve-shaped main body 10 tworeceiving spaces for spring elements 15, preferably cylindrical rubberstops, whose dimensions and spring stiffness are selected such that alimited relative movement between the fastening element 13 and the mainbody 10 about a defined vertical axis defined by the axle pin 11 isprovided.

1.-31. (canceled)
 32. A backrest for a stool or a chair, the backrestcomprising: a first and a second substantially L-shaped support memberseach comprised of a first leg and a second leg, wherein the first legsform a carrier part, respectively; a first and a second back supportseach arranged in a springy fashion and arranged laterally adjacent toone another; wherein the first and second back supports are attached tothe carrier parts; wherein the second legs are attached below a seat ofthe stool or the chair so as to be pivotable against a spring forceabout a horizontal pivot axis; wherein the first and second supportmembers are connected to one another by a guide bar that is orientedsubstantially perpendicularly to the first and second support members ina rest position of the first and second support members, which guide baris supported in or on a seat understructure and connected to the firstand second support members such that upon movement of one of the firstand second back supports in a first direction to the front or to therear of the stool or the chair the other one of the first and secondback supports is moved in a second direction opposite to the firstdirection, respectively.
 33. The backrest according to claim 32, whereinthe guide bar has ends that are pivotably connected to the first andsecond support members, respectively, by a ball joint that is supportedin an elastically deformable sleeve.
 34. The backrest according to claim33, wherein the guide bar is supported at a connecting point between theends connected pivotably to the first and second support members on theseat or a seat understructure.
 35. The backrest according to claim 34,wherein the guide bar is supported by a ball joint at said connectingpoint between the ends.
 36. The backrest according to claim 32, whereinthe guide bar is guided in arc-shaped guide grooves provided in or on aseat understructure, wherein imaginary axes of the arc-shaped guidegrooves extend parallel to the horizontal pivot axis of the first andsecond support members and, relative to the front end of the chair, arecurved from the top to the rear and from the rear to the bottom.
 37. Thebackrest according to claim 33, wherein the guide bar is connectedpivotably to the second legs of the first and second support members.38. The backrest according to claim 37, wherein the second legs eachhave an upwardly oriented projection and said projections are supportedby first springs that, in the rest position of the first and secondsupport members, are uniformly pressure-loaded.
 39. The backrestaccording to claim 38, wherein the first springs are coil springs whoselongitudinal axis are perpendicular to the horizontal pivot axis of thefirst and second support members and are arranged in the area of theseat understructure.
 40. The backrest according to claim 39, furthercomprising pressure plates mounted on the projections and supported byplungers on first springs.
 41. The backrest according to claim 38,wherein the pretension of the first springs is changeable.
 42. Thebackrest according to claim 41, wherein the first springs have endsopposite the pressure plates and said ends rest against blocks movablein a longitudinal direction of the first springs, wherein the blocks aresupported on cams of a camshaft which camshaft is turnable from theexterior.
 43. The backrest according to claim 42, wherein said guide baris attached to a seat understructure supported by second springs suchthat the seat understructure upon pivoting of the first and secondsupport members is movable to the front or to the rear relative to aseat frame.
 44. The backrest according to claim 32, wherein the backsupports are attached in a springy fashion on the carrier parts.
 45. Thebackrest according to claim 32, wherein the back supports are attachedto the carrier parts so as to be pivotable about a substantiallyvertically oriented axis, respectively.
 46. The backrest according toclaim 32, wherein the back supports are positionable along the carrierparts at different height positions.
 47. The backrest according to claim46, wherein the back supports are attached to securing members that areslidable along the carrier parts.
 48. The backrest according to claim47, wherein the securing members each have a body attached thereto so asto be pivotable against a first spring force about a horizontal axis,wherein said bodies are attached to the back supports, respectively, soas to be pivotable against a second spring force about a vertical axis.49. The backrest according to claim 32, wherein the first and secondback supports are connected to one another by an elastically deformabletransverse stay and wherein a strength of the transverse stay isselected such that the first and second back supports function asindividual supports and a movability of one of the first and second backsupports relative to the other one of the first and second back supportsmaintained to a limited extent.
 50. Chair furnished with a backrestaccording to claim
 32. 51. Seating furniture comprising a seat, asupport unit, and a column, wherein the seat is attached with saidsupport unit to the column, and further comprising a backrest that hastwo back supports that are arranged laterally adjacent to one anotherand secured in a springy fashion, wherein the backrest further has afirst and a second substantially L-shaped support members each comprisedof a first leg and a second leg, wherein the first legs form asubstantially vertically extending carrier part, respectively, andwherein the two back supports are attached to the carrier parts andwherein the second legs are attached below the seat so as to bepivotable against a spring force about a horizontal pivot axis, whereinthe support members each have a separate spring element.
 52. Seatingfurniture according to claim 51, wherein the force of the springelements acting on the support members is jointly changeable. 53.Seating furniture according to claim 51, wherein the second legs of thesupport members are configured as a two-arm lever, wherein the springforce acts on a free lever end of the two-arm lever.
 54. Seatingfurniture according to claim 53, wherein the spring force is effected bya spring element that is substantially oriented vertically.
 55. Seatingfurniture according to claim 53, wherein a free lever end of the two-armlever of the second leg has a bent section oriented upwardly ordownwardly, wherein an essentially horizontally oriented spring elementacts on the bent section.
 56. Seating furniture according to claim 55,wherein the bent section is oriented upwardly and wherein the springelement is a tension spring and wherein ends of the tension springs ofthe support members are attached to an adjusting member that issecurable relative to the horizontal pivot axis at different spacingsfor changing the force acting on the support members.
 57. Seatingfurniture according to claim 51, wherein the back supports each areattached height-adjustably on the carrier parts, respectively. 58.Seating furniture according to claim 51, wherein the back supports eachare attached in a springy fashion on the carrier parts, respectively.59. Seating furniture according to 58, wherein the back supports eachare pivotable relative to the carrier parts about a horizontal axis,respectively.
 60. Seating furniture according to claim 58, wherein theback supports are pivotable about a vertical axis relative to thecarrier parts, respectively.
 61. Seating furniture according to claim58, wherein the back supports are attached to securing members that aresecurable along the carrier parts, respectively, at different heightpositions.
 62. Seating furniture according to claim 61, wherein the backsupports each are attached by intermediate positioning of at least onelastically deformable spring element on the securing members,respectively.
 63. Seating furniture according to claim 62, wherein thesecuring members each have a body attached thereto so as to be pivotableagainst a first spring force about a horizontal axis, wherein saidbodies are attached to the back supports, respectively, so as to bepivotable against a second spring force about a vertical axis. 64.Seating furniture according to claim 51, wherein the support members arefixedly securable at different spacings from one another along thehorizontal pivot axis.